1. Field of the Invention
The present general inventive concept relates to a semiconductor memory device.
2. Description of Related Art
Semiconductor memory device may be a storage unit to store data and output the stored data as necessary or as desired. Semiconductor memory devices may be classified into non-volatile memory devices and volatile memory devices.
The volatile memory devices may be a memory device that loses stored data without power. The volatile memory devices may include SRAM, DRAM, SDRAM, or the like. The non-volatile memory devices may be a memory device that retains stored data even without power. The non-volatile memory devices may include ROM, PROM, EPROM, EEPROM, flash memory device, FRAM, PRAM, MRAM, RRAM, and the like.
Flash memory devices may be classified into a NAND flash memory device and a NOR flash memory device based upon interconnection between memory cells and bit lines. The NAND flash memory device may be used as a mass storage unit.
Memory cells of a flash memory device may include floating gates or charge trap layers placed between a bulk area and control gates. The flash memory device may store data by adjusting threshold voltages of memory cells via accumulation of charge on floating gates or trapping charge on charge trap layers. Accurate control of threshold voltages is desirable in flash memory devices.